Refrigeration systems, particularly commercial and industrial refrigeration systems, may have a single compressor though these systems often include a number of refrigerant compressors. Typically, there are enough compressors to accommodate the anticipated peak load to be placed on the refrigeration system. However, most refrigeration systems operate at peak load for only a few hours out of the year and spend most of the time operating at a load point less then the peak design load. As such, it is desirable to be able to modulate the capacity of the refrigeration system to save energy and reduce operating costs when the load on the refrigeration system decreases.
In other conventional refrigeration systems, the compressors are unloaded using a gas bypass system. In a gas bypass system, compressed refrigerant is recirculated from the discharge side of the compressor back to the suction side of the compressor. However, with this method of compressor unloading, the energy expended to compress the refrigerant is wasted each cycle that the refrigerant is recirculated back to the suction side of the compressor, thus reducing overall system efficiency. As a result, maintaining and operating the types of conventional refrigeration systems described above can be costly.
Embodiments of the invention represent an improvement in the state of the art for single-compressor and multiple-compressor refrigeration systems. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.